How early settlers unwittingly
drove their nemesis extinct, and what it means for us
today

Picture swirling snow as far as the eye
can see — in the middle of summer. Now, imagine this blizzard
of flakes transforming into a swarm of locusts. This isn’t
just any swarm, but the largest congregation of animal life that
the human race has ever known. Picture yourself in Plattsmouth,
Neb., in the summer of 1875.

A swarm of Rocky Mountain
locusts streams overhead for five days, creating a living eclipse
of the sun. It is a superorganism composed of 10 billion
individuals, devouring as much vegetation as a massive herd of
bison — a metabolic wildfire that races across the Great
Plains. Before the year is up, a vast region of pioneer agriculture
will be decimated and U.S. troops will be mobilized to distribute
food, blankets and clothing to devastated farm families.

I
came across an account of this staggering swarm in the Second
Report of the U.S. Entomological Commission, published in 1880. By
clocking the insects’ speed as they streamed overhead, and by
telegraphing to surrounding towns, Dr. A.L. Child of the U.S.
Signal Corps estimated that the swarm was 1,800 miles long and at
least 110 miles wide. This suffocating mass of insects was almost
large enough to cover the entire states of Wyoming and
Colorado.

Swarms like this — albeit usually on a
smaller scale — are part of the life cycle of locusts around
the world. At low population densities, these insects behave like
typical grasshoppers, to which they are closely related. But when
crowded, this insectan Dr. Jekyll transforms into Mr. Hyde.
Chemical cues from their feces and frequent disturbance of tiny
hairs on their hind legs set off the changes. The changelings
aggregate in unruly mobs, feed in preference to mating, grow longer
wings and a darkened body, and irrupt into rapacious
swarms.

It is as if whenever humans found that our
neighborhoods smelled like sewers, and that we were constantly
jostled on the way to work, we abruptly changed into throngs of
anxious, red-faced neurotics with an inexplicable desire to buy a
plane ticket or rent a U-Haul. Perhaps locusts and humans have more
in common than we suppose.

This metamorphosis is probably
a survival mechanism. In temperate ecosystems, locusts outbreak
when droughts cause their verdant habitats to shrink, forcing the
insects into crowded masses and signaling that it’s time to
escape impending disaster. The swarms are like the Mongol hordes
that once swept across the steppes in search of new lands. The
immense clouds of Rocky Mountain locusts are the subject of
frontier legend. Laura Ingalls Wilder’s On the Banks of Plum
Creek revolves around the devastation wreaked by a locust swarm
that descended on her family’s land:

"The cloud was
hailing grasshoppers. The cloud was grasshoppers. Their bodies hid
the sun and made darkness. Their thin, large wings gleamed and
glittered. The rasping whirring of their wings filled the whole air
and they hit the ground and the house with the noise of a
hailstorm. "Laura tried to beat them off. Their claws clung to her
skin and her dress. They looked at her with bulging eyes, turning
their heads this way and that … Grasshoppers covered the
ground, there was not one bare bit to step on. Laura had to step on
grasshoppers and they smashed squirming and slimy under her feet
…

" ‘The wheat!’ Pa shouted."

Today, this is hard to imagine; it sounds like an old Alfred
Hitchcock thriller. But if we find it difficult to envision such
masses of life, it is even more challenging to grasp that within 30
years of Dr. Child’s account of the largest insect swarm ever
recorded anywhere, this species disappeared — forever. The
last living specimen of the Rocky Mountain locust was collected in
1902 on the Canadian prairie.

But if we pay careful
attention, the Rocky Mountain locust has lessons to teach us about
abundance and extinction and our tendency, as a species, to stumble
like bulls through nature’s china shop. Perhaps most
importantly, the locust has troubling implications for contemporary
society, and warnings about our future in a fast-changing
landscape.

In 1986, I was hired as an insect ecologist at
the University of Wyoming to explore the world of grasshoppers
— a mission I’ve undertaken for the past 17 years. No
sane person would devote so much time to pursuing a subject that
did not touch the heart and soul while stimulating the mind. And
I’ve found that grasshoppers hold mysteries and lessons that
are worthy of this labor of love.

The science of
entomology is an arcane discipline, and the story of the locust was
peripheral even there. But the story had floated about for many
years, and fascinated me because of what was missing as much as
what it contained.

Soon after arriving at the
university, I learned that the accepted explanation for the
locust’s demise was a vague conspiracy of vast ecological
changes. Entomologists proposed that the disappearance of bison,
the decline of fires set by Indians, and changes in climate had
altered the locust’s prairie habitats. But when I started
digging through the evidence, none of these factors provided a
satisfactory explanation.

The mystery was so intriguing,
and the existing explanations so full of holes, that I was
compelled to reopen the case. Besides, I had a lead on a bounty of
clues that had scarcely been touched. Digging through old, obscure
geological reports, I learned about the existence of "grasshopper
glaciers," strung along the spine of the Rockies. Curious, I did
more research, and learned that these glaciers were so named
because of their contents — they had entombed wayward
grasshopper swarms centuries ago. If the grasshopper corpses were
actually locusts, they might provide a clue as to how these insects
disappeared.

At first, it looked like the search for clues
would be futile. My students and I started at Grasshopper Glacier
above Cooke City, Mont., which had once been promoted as a tourist
attraction, accessible by horse, and later, by jeep. The insects in
that glacier were badly decomposed, as the ice had been melting.
Another Grasshopper Glacier in the Crazy Mountains yielded
beautifully preserved grasshopper specimens, but they were no more
than a few years old.

For the next two years, we searched
the ice plastered on the flank of Beartooth Peak, near the Wyoming
border. Again, we collected the mangled body parts of long-dead
grasshoppers and honed our forensic skills. The fragments matched
those of the Rocky Mountain locust, but we lacked the definitive
evidence that could only come from intact, whole bodies.

Finally, after four years of fruitless
searching, following up on a tip from colleagues at Western Wyoming
Community College, we found the mother lode. High on Knife Point
Glacier in the Wind River Mountains, with Gannett Peak looming in
the distance, a frozen graveyard was emerging through the ice. The
tiny bodies had been crushed, but they were intact. There was no
doubt that these were the corpses of Melanoplus spretus. We’d
found the locust.

We eventually recovered 130 largely
intact remains. Each was catalogued, dried for preservation, and
individually stored for future study. Based on subsequent
radiocarbon dating and analysis of the glacier, we surmised that in
the early 1600s — around the time that the Pilgrims landed at
Plymouth — a swarm of Rocky Mountain locusts was blown into
the mountains, probably from the river valleys 100 miles to the
northwest that are now part of Yellowstone National Park.

Scattered across the glacier in a seething carpet of brown-green
bodies, some of the locusts may have escaped and continued their
journey, but millions were probably immobilized by the cold. In the
course of summer melting, rivulets washed them into the crevasses
that split the top of the ice field. With time, they were frozen
deep in the glacier and slowly transported down the side of the
mountain.

Today, about 750 feet downhill from the
crevasses, the slope flattens rather sharply, and the ice —
in a slow-motion version of the rapids at the base of a waterfall
— becomes turbulent, churning its contents to the surface.
For the first time in nearly 400 years, the locusts have come back
into the light.

The study of their corpses, along with
careful historical research and ecological sleuthing, allowed us to
slowly piece together the story of a remarkable creature. Perhaps
most interesting, the story of the locusts challenged a basic tenet
of conventional ecological wisdom.

The standard textbooks
of applied entomology suggest that insect outbreaks are evidence of
a disturbed or out-of-balance ecosystem. Like a well-behaved child
or a good worker, a species should refrain from extreme outbursts.
This Victorian-era view of the ideal emotional state —
perhaps also the legacy of Darwinian uniformitarianism, which
emerged as a reaction to the church’s reliance on
catastrophes to explain the history of the Earth — has lived
on in our perception that an outbreak or crash of population is a
sign of a troubled species.

Not so with the Rocky Mountain
locust. The leitmotif of this insect was its phenomenal flights of
reproductive fancy, with manic swarms sweeping over the Plains only
to subsequently collapse into pockets of exhausted survivors.
Evidence of this was embedded in the annual layers of Knife Point
Glacier, which revealed a pattern of locust outbreaks extending
centuries prior to European alterations of the Western
landscape.

All too often, we are alarmed by
nonconformity because of our desire to live in a predictable world,
our social and political intolerance of radicalism, our economic
pursuit of steady growth, and our Protestant ideal of moderation.
It is true that people, species and ecosystems can manifest extreme
dynamics during times of trouble. But the locust shows that
erratic, even explosive, population dynamics do not necessarily
reflect dysfunctionality – nor do they require meddling from
humans.

I suppose I shouldn’t have been surprised
that our work on the Rocky Mountain locust was at first met with
skepticism.

Along with my students and
colleagues, I submitted our work to a scientific journal; the paper
described what we had found, including the condition of the
glacier, the location of deposits, the types of insect parts we had
extracted, the radiocarbon dating, and the analysis that led us to
believe we had recovered the remains of the Rocky Mountain locust.
As the first study of insects exhumed from a glacier in nearly 50
years, we hoped that the manuscript would be well received. It was
rejected.

On behalf of the reviewers, the editor explained
that the study did not constitute a controlled experiment. "You
have mistaken natural history for science," she wrote. But I
suspect that the reviewers’ doubts ran deeper. One of the
long-lasting debates surrounding the Rocky Mountain locust had been
whether it was truly a species or simply the migratory form of a
species that still exists but no longer swarms. The arguments were
phrased in terms of scientific evidence, but I could not help
wondering if the debate was grounded in a visceral disbelief that
such an enormously abundant creature could disappear from the face
of the earth in a matter of a few decades.

I could
understand the misgivings. The glacier had revealed a great deal
about the life of the Rocky Mountain locust, but frustratingly
little about its death.

At the time of the insect’s
disappearance, there were no synthetic carbon-based pesticides, no
modern earth-moving equipment, not even chain saws. Settlers fought
back with what tools they had, from flooding to fire to dynamite.
But this hand-to-hand combat didn’t make a dent against an
enemy that was billions strong. So one could only conclude that if
humans had wiped out the Rocky Mountain locust, they had done so
inadvertently. In other words, the most spectacular "success" in
the history of economic entomology — the only complete
elimination of an agricultural pest species — was a complete
accident.

How could an unwitting cohort of early
settlers, concentrated in a relatively limited area of the vast
Great Plains and Rocky Mountains, have wiped out an insect that
during its outbreaks ranged from Canada to Mexico and from Utah to
Iowa?

The break in the case came during my teaching. In an
effort to work some interesting (i.e., nonmathematical) elements
into my Insect Population Biology course, I dug into the ecology of
the monarch butterfly. Much like the locust, this species
distributes itself across the face of the continent. And much like
the locust, the monarch is poised on the edge of extinction in
North America.

How could a butterfly that fills roadsides
and fields from Texas to Maine be in jeopardy? After migrating
northward each summer, this species returns to overwinter in the
remote mountains of Mexico. Its populations stretch across North
America, only to collapse back into a few shrinking pockets of
forest. Loosed on these pockets, a logging crew armed with chain
saws could put an end to this magnificent butterfly in a matter of
weeks.

There was the answer, staring me in the face. Like
the monarch butterfly, the Rocky Mountain locust was tremendously
vulnerable at certain times in its life. Between outbreaks, the
locust hid out in the river valleys of Wyoming and Montana —
the same river valleys that settlers had discovered were best
suited for farming.

By converting these valleys into farms
— diverting streams for irrigation, allowing cattle and sheep
to graze in riparian areas, and eliminating beavers and their
troublesome dams — the pioneers unknowingly wiped out locust
sanctuaries. They destroyed the locust’s equivalent of
Mexican forest wintering grounds. They doomed the species.

I’d pretty well wrapped up the case of
the locust’s disappearance. Our studies were eventually
published in respected scientific journals, and my explanation of
the locust’s extinction became the most widely accepted
theory.

But I was not quite ready to give up on finding a
few still alive. Although it was a long shot at best, in the 1990s
my students and I ventured into the last possible haunts of the
locust, the river valleys near Yellowstone National Park where the
soils had never been turned, cattle had never grazed, and the
waters still flowed freely. Few entomologists had systematically
collected grasshoppers in these remote valleys, so a glimmer of
hope remained. Until I had tried and failed to find this creature
on my own, I was reluctant to declare that it had truly vanished
from the face of the earth.

As we scoured the meadows
along the Yellowstone River, armed with sweep nets, I imagined what
might happen if we found a lost population of locusts. Regulatory
officials might advocate their destruction, fearing a revival of
the swarms of the 1800s. Even the vaunted Endangered Species Act
exempts pests from protection, so this remnant population might
well be accorded the same status as the last vials of
smallpox.

However, in my fantasy scenario, I liked to
imagine — not without irony — that economic
entomologists would point out that "pest" is a label that can be
applied only under appropriate conditions: A population of Rocky
Mountain locusts that had not bothered us for a hundred years could
hardly be termed a pest. From the environmental camp, a few voices
might call for protecting these insects as important components of
a native ecosystem. Some might point out that the Rocky Mountain
locust could serve as a reminder that humans have to share this
world with other species — including those that we have not
tamed or controlled. Others might cite its powerful place in the
history and folklore of the West.

But in the end, I
wondered, would our decision be any different from that which the
early pioneers would have made, had they realized that they had
reduced the locust to a tiny final fragment of habitat? If we
struggle so mightily over whether we should save the last bits of
old-growth forest and the few untrammeled tracts of the Arctic,
what hope would a locust have?

As word of our search
spread, a few leads developed. At one point, there was a report of
a number of grasshopper specimens collected in North Dakota that
were similar to the Rocky Mountain locust. But they turned out to
be the migratory phase of another, closely related grasshopper
species. In the end, we came up empty-handed. While my heart keeps
me half-looking for survivors whenever I hike the river valleys
that cut through the Rocky Mountains, my head has given the locust
up for dead.

We usually conceive of the world in terms of
material things — for example, we define a species as a bunch
of individuals with the capacity to successfully interbreed.
Ecology, however, is beginning to slowly shift focus, tentatively
exploring what the world would look like if process, rather than
matter, were the basis for reality. What if we defined a species in
terms of its life processes? What if we suggested that a thing is
what it does?

In this light, the Rocky
Mountain locust was an immense, aperiodic process of energy flow,
linking life-processes across a continent. And in this light, there
is no doubt that this species was extinct by the late 1800s. Even
if I found a remnant population and we managed to conserve the last
Rocky Mountain locusts in a zoo, they would no more be their
original species than the condors that can never again know the
vast, unbroken expanses of California’s foothills. Unless
these insects could once again blacken the skies of the West, they
would, in fact, be nothing more than Rocky Mountain
grasshoppers.

Setting aside the current wave of
extinctions, the average species of bird or mammal has a life
expectancy of about 10 million years, according to ecologist E.O.
Wilson. If this is true, Homo sapiens is still in its adolescence
— a time during which individuals of our species pay little
heed to their own mortality. To teenagers, the notion of dying is
hopelessly irrelevant, a fact that must contribute to the foolish
indiscretion, misplaced courage and irrational risk-taking that too
often end in accidental death.

Our species seems to be
manifesting these same tendencies at this point in its development.
But there are older, wiser voices to be heard in our biological
community, including that of the Rocky Mountain locust. Dr.
Child’s record swarm of 1875 probably contained in the
neighborhood of 10 billion insects, which is disconcertingly close
to the current human population on the planet. Having reached 6
billion people, we need only look back at the locusts that once
blackened the skies of North America to realize that the future of
a species is no brighter for its great
numbers.

But, you might argue, human beings
are the ultimate generalists, capable of adapting to a wide range
of environmental challenges or, if times get really tough, of
moving on to the next best place. However, the Rocky Mountain
locust was also a generalist that consumed no fewer than 50 kinds
of plants from more than a dozen different families, not to mention
— when hunger demanded — leather, laundry and wool
still on the sheep. In contrast, human beings derive most of our
food from just three plant species — corn, wheat, and rice
— found in a single family.

Moreover, if the body
size of the Rocky Mountain locust was increased to that of a human,
available records suggest that it would be capable of traveling
36,000 miles — approximately the circumference of the Earth.
It appears that being a highly mobile generalist is little
protection against extinction.

Still, the
Rocky Mountain locust had an Achilles’ heel — the
ecological bottleneck that allowed a small contingent of settlers
equipped with horse-drawn plows, axes, and shovels to do them in.
Humans don’t seem to have this sort of bottleneck. Or do
we?

On our last day on Knife Point Glacier, my students
and I set a drift net in one of the hundreds of rivulets that
rushed down the face of the ice. In just 24 hours, we collected 140
fragmented remains of the Rocky Mountain locust. At this rate, at
least 20 million corpses have melted from the glacier since that
day in 1990, washing into Dinwoody Creek and from there, perhaps,
into the Wind River.

It’s not just the churning of
the glaciers that is bringing locusts back into the light. The
glaciers of the Rocky Mountains are melting at a phenomenal rate.
Based on our studies of Montana’s grasshopper glaciers, the
glacier north of Cooke City has receded 89 percent since 1940; the
glacier in the Beartooth Mountains is 62 percent smaller now than
in 1956; and the one in the Crazy Mountains has diminished 90
percent in the last 16 years.

Our discovery of grasshopper
remains coming to the surface of these glaciers is a direct result
of global warming.

As ecological processes on the planet
change through human activity, we find ourselves increasingly
brought into conflict. Shifts of human populations away from
flooded seaboards and desertified landscapes, burgeoning
populations in cities and their marginal slums, wars over oil,
struggles for access to water, and fights to save remnants of
disappearing habitats are all on the horizon.

In these
troubled times, sociologists tell us that humans increasingly seek
solace. We are drawn to our sacred spaces: churches, synagogues,
temples and — for some of us — serene mountain valleys,
where rivers cleanse our anxious minds. Just as the locust was able
to find a safe refuge, where it could rest and revitalize, we need
our sanctuaries. But is it possible that these very havens —
our wilderness preserves, ungrazed meadows, clear streams —
might prove to be ecological bottlenecks?

A century ago,
human alterations of the environment caused the demise of the Rocky
Mountain locust, and today, the ghosts of these insects warn us of
an even more serious threat to the natural world. As our current
environmental crisis exposes our past act of accidental
destruction, one can only wonder what else we can learn from the
Rocky Mountain locust.

Jeffrey Lockwood is
Professor of Entomology in the Department of Renewable Resources at
the University of Wyoming.